Post nasal drip can cause bad taste in the throat apart from that feeling of mucus in the throat .Sinusitis is the common cause of post nasal drip but apart from that acid reflux can also cause PND .
If their is associated acid reflux then you should try to treat this underlying cause .
Trapped food particles between the teeth, tooth decay can cause foul odour.So it is important to maintain a good oral hygeine and since you have problem with bad breath a dental check up should also be considered apart from maintaining good oral hygeine .
Also taking some medicines like metronidazole etc can also cause bad taste in mouth .
Hope this helps
Acid reflux , Dryness in the mouth , problems with tonsills are some of other condition which may cause bad breath .
Drink plenty of water .
Brush twice a day .Also tounge cleaning should also be done appropriately. Use of mouth wash should also be considered .Avoid smoking and alcohol .
Also some times GIT related problems like constipation can cause bad breath .
Post nasal drip and acid reflux can be a possibility .
Some medications are also responsible for this symptom .
Check this link for a detailed list of possible causes